1. Field of the Invention
The present invention relates to an image recording method for forming an image on a recording medium using an ink.
2. Discussion of the Background
Inkjet recording methods have advantages such that color images can be easily recorded; and the running costs are relatively low. Therefore, various research and development concerning recording devices, recording methods, inks and recording media have been made. As for the recording medium, swelling type recording media and void-structure type recording media have been developed. Among these recording media, void-structure type recording media are mainly used because of being superior in ink drying speed.
Void-structure type recording media typically have a structure such that an ink absorbing layer having voids for absorbing ink droplets is located on a substrate, and an optional porous gloss layer is located on the ink absorbing layer. Since the recording media have such a structure, the recording media have not only excellent ink absorbing property but also a combination of glossiness and appearance quality better than those of conventional photographic papers, and can produce high definition images. However, since fillers having a large oil absorption (i.e., a large specific surface area) have to be used as the filler included in the ink absorbing layer of the void-structure type recording media to impart good transparency to the ink absorbing layer, a large amount of expensive filler such as silica, alumina hydrates, colloidal silica has to be used, resulting in increase of costs of the recording media. In addition, since the method for preparing such void-structure type recording media is complex, the recording media have much higher costs than conventional photographic papers.
In addition, inkjet recording media have another drawback such that images formed thereon are damaged relatively easily compared to photographic images. This is because the photographic images are formed in a coloring layer of a photographic paper, which layer is located in an inner portion of the paper and is covered with a protective layer (i.e., gelatin layer). Therefore, even when photographic images are strongly rubbed, the images are hardly damaged. In contrast, in the case of inkjet recording media, images are formed on the surface or in a surface portion of the recording media. Therefore, it is difficult for the images formed on such inkjet recording media to have the same durability (i.e., resistance to rubbing) as that of photographic images. Among various images recorded by inkjet recording methods, images recorded by dye inks, which tend to penetrate into recording media, have relatively good rubbing resistance. However, since images recorded by pigment inks tend to be present on the surface of the outermost layer of recording media, the images have relatively poor rubbing resistance compared to the dye ink images.
Recently, in addition to consumer applications, inkjet recording methods need to be used for applications for small amount of copies, and variable print applications (such as commercial photographic printing) such that a document is distributed to persons while changing the contents of the document. However, because of the drawbacks mentioned above, the inkjet recording methods cannot fulfill the needs for costs and durability. Therefore, inkjet recording methods are not widely used, although high quality images can be produced thereby.
In contrast, offset printing methods, which use a lipophilic ink, are used for commercial printing fields because cast coated papers, which are glossy like photographic papers and which have low costs, can be used as the recording medium. The reason why cast coated papers have low costs is that the materials used for the coating layer thereof have very low costs, and the method for preparing the cast coated papers are relatively simple (i.e., the method has a high productivity) compared to the method for preparing the recording media used for inkjet printing. These cast coated papers are designed assuming that images are formed thereon by offset printing.
When images are formed on such cast coated papers by inkjet printing, the inks are not absorbed well, thereby causing problems such that the recorded images blur, and it takes a long time until the recorded images dry. Therefore, cast coated papers cannot be used as recording media for inkjet printing. In addition, since cast coated papers do not include a cationic fixing material, images recorded thereon by inkjet printing have low reliability. Specifically, problems in that recorded images are blurred when contacted with water; and recorded images are faded by ozone are caused.
In addition, since the colorants included in recorded images tend to stay on the surface of cast coated papers, problems in that the even when slightly rubbed, the images are damaged (i.e., the colorants peel off the cast coated papers, resulting in disappearance of the images, change of the color of the images, or transfer of the colorants to other portions of the images) are caused.
In commercial printing, the printed images are typically required to have good abrasion resistance and high glossiness. Therefore, UV coating tends to be performed on the recording media. Specifically, recording media used for commercial printing typically have a transparent layer, which is prepared by applying a so-called UV varnish, i.e., an OP (Over Print) varnish including an UV crosslinkable material. Since UV varnishes can be quickly dried by an UV lamp, the UV varnishes are widely used for printing fields. Since UV LEDs having low power consumption have been developed now, the devices can be used for crosslinking the coated layer instead of UV lamps. Therefore, an increasing need exists for such UV varnishes.
Published unexamined Japanese patent application No. (hereinafter referred to as JP-A) 2004-330570 discloses a printing device having a pre-treatment processing section configured to prepare an ink receiving layer on a recording medium; an inkjet processing section configured to perform inkjet recording; and a post-treatment processing section configured to apply an UV varnish on the recording medium bearing the recorded image thereon. However, when an UV varnish is applied on an ink receiving layer formed on a recording medium, the following problems tend to be caused:    (1) A uniform layer cannot be formed by applying a UV varnish on such an ink receiving layer (i.e., the resultant recording medium has uneven appearance); and    (2) The UV varnish applied on such an ink receiving layer cannot be well crosslinked (i.e., the coated UV varnish remains on the ink receiving layer without being crosslinked), thereby causing problems in that the recording medium is tacky, and emits foul smell.
JP-A 2005-329713 discloses a technique in that an UV crosslinkable liquid having a low viscosity is ejected from an inkjet nozzle to form an overcoat layer. This technique is preferably used for forming a glossy portion in a print, but is unavailable for a case where the glossing treatment is performed at a high speed on the entire surface of recording media bearing a recorded image thereon. When this technique is used for inkjet recording, the following problems are caused:    (1) The glossiness of the resultant recorded image (or the recording medium) is low, and therefore a large amount of coating liquid is needed to impart a high glossiness to the recorded image, resulting in increase of the running costs; and    (2) The resultant overcoat layer is imperfectly crosslinked.
Thus, this technique cannot be used for inkjet printing, which is required to produce prints at low costs.
JP-A 11-277724 discloses a technique in that after an image is formed on a recording medium having poor ink absorbing property, UV coating is performed thereon. However, when a recording medium having poor ink absorbing property is used, ink images formed thereon blur and/or are not quickly dried particularly when pigment-type aqueous inks are used. Specifically, when pigment-type aqueous inks are used, clear images cannot be formed because images formed on a recording medium, which are not dried perfectly, are blurred by the overcoat layer coating liquid applied thereon. Thus, this technique cannot be practically used.
As mentioned above, it is considered to be difficult to prepare a print by combining the techniques of offset printing, inkjet recording, and OP varnish treatment (particularly UV varnish treatment). Specifically, it is difficult to form a glossy print (like photographic prints) at low costs using a method, in which after the background thereof is printed by offset printing, an image (such as figure images) is formed thereon by inkjet recording, and then an OP varnish treatment is performed thereon.
Because of these reasons, a need exists for a recording method, which can produce high quality images, which have a good combination of glossiness and abrasion resistance like photographic prints, at low costs.